Overview

Emacs for GNUstep and MacOS X is a version of
GNU Emacs CVS unicode-2 branch (currently planned to be released as
Emacs 23) which adds support for the GNUstep and MacOS X systems via
the OpenStep APIs (referred to as "Cocoa" under OS X).
– From the manual.

Features

This port leaves most of the core functions of Emacs unchanged and is
fully-compatible with all Emacs Lisp packages, however it has a number
of step-ish features which do not have any equivalent in Emacs's X11
interface. The design aim was to make it look as similar as possible
to an X application to Emacs Lisp programs and to make it look like a
normal GNUstep or MacOS X application to users.
– From the manual.